A patent pending ammonia-based hydrometallurgical method is developed to selectively leach nickel coatings from the Nickel-Plated Steel sheets (NPS). The leaching process starts with the removal of the passive nickel oxide film by Na2S2O3.5H2O addition into the solution, followed by the dissolution of the metallic nickel. Leaching stops due to the passivation of the diffusion region between the coating and the steel. The experiments were conducted using two different ammoniacal systems, the NH3-(NH4)¬2S2O8-Na2S2O3.5H2O and the NH3-(NH4)¬2SO4-Na2S2O3.5H2O system, resulting in leaching efficiencies of 98% and 91% respectively.

In the current industrial age the amount of secondary material resources is expected to increase at a fast rate. Within the steel supply of these secondary resources, the share of End-Of-Life(EOL) scrap will become bigger over time compared to new industrial scrap.
The waste stream of EOL steel scrap is heterogeneous and contaminated, complicating existing recycling routes used for industrial scrap. A way to combat the contamination is to apply heat treatment to the EOL scrap. This study investigates the implications of heat treatment on EOL tinplate, a tin coated steel product used for packaging.
Tin is considered a tramp element in a steel melt, thus the coating must be removed before recycling. Heat treating tinplate causes the tin coating to form an intermetallic alloy with the steel substrate, as a result tin atoms become more difficult to separate from the steel scrap product.  The reduction/oxidation behaviour of the two most prevalent tin-iron intermetallic alloys, FeSn2 and FeSn, has been mapped through Cyclic Voltammetry(CV) in both an alkaline and acidic electrolyte. Pure tin and the steel substrate of tinplate scrap were similarly investigated to compare all elements in the system. The goal is to achieve if selective separation and recovery of tin. Further analysis of the anodic dissolution through Chronoamperometry(CA) analysis allow insight in how the current response over time. Based on the CA results, a detinning process is tested over trials of new industrial scrap and EOL municipal scrap. The process has a high detinning rate for new scrap, while for EOL scrap the detinning is hindered by a presence of paint or lacquer. Trials on heat treated EOL scrap showed a small reduction of the negative impact of lacquers and paint. At the same time it was observed that most of the free tin transformed into FeSn2.
The data from Cyclic Voltammetry, Chronoamperometry and detinning trials were used to propose a possible detinning line design for heat treated EOL tinplate scrap.

Aluminium recycling is a crucial process when it comes to recycling of metals. To make the metal industry part of a circular economy, this process must be efficient and for the interest of companies it should be economical. Singulation is such a process which does both the tasks. In this work, aluminium scrap recycling has been positioned as a commercially beneficially process which encourages companies to take up the process and since the process is environmentally advantageous as well, there has been mentions of how the authorities provide policies which support this process. The first part of the work looks at how and why aluminium is produced which looks into the processes such as Bayer and Hall-Heroult and into multiple uses of the aluminium alloys and also mildly touches upon some of the compatible alloy series. Aluminium is a highly recyclable material so it is interesting to study about what happens one it has reached its End of Life (EOL) stage. Sorting is an essential stage in the recycling of aluminium and there are solutions which encourage sorting based on alloy series which again is economically and ecologically beneficial. And for this to happen efficiently, singulation is essential. Singulation of aluminium is important to achieve better efficiency in the process of recycling which is the aim of companies such as Reukema. Although useful, singulation has many challenges. Since it is a solution which depends on the problem i.e., there is no universal way to singulate every kind of material, the problem here has challenges such as entangling of material, their landing on top of each other are just some of such problems which are looked at here. By simulation, it was found that the arrival pattern of the material follows a homogenously random distribution for smaller size fraction but a highly regularized distribution for large size fractions but smoothens to a homogenously random distribution as we increase the number of particles for both size fractions. The experiments performed after developing a time series were compared to a simulated singulation process and the results were not ideal in terms of singulation since the chute was not included in the process. The experimental setup needed to be optimised which could lead to even better and accurate results. Higher particle speed on the vibrating feeder could have played a crucial role.

Jarosites are an Fe-rich waste product from the Zn industry. They contain toxic heavy metals like Pb, Zn, Cu, Ni, and are consequently disposed of in regulated ponds. With Zn demand projected to continually increase in the future, it is anticipated that by 2023, the Fe content in these jarosites will amount to 2.2 million tonnes/year. With the advent of the circular economy and raw materials scarcity it has become imperative that ’wastes’, like jarosite, are converted to resources. Since jarosites are Fe-rich, they can be used for ironmaking. HIsarna is a revolutionary ironmaking process that has greater flexibility in the raw materials it uses. It can potentially utilise jarosite, which was unsuitable for a conventional blast furnace, to make hot metal. However, steelmaking, which occurs downstream of HIsarna ironmaking, requires the removal of Cu, Ni, Cr, Sn and Mo (termed CEF metals). Removal of these CEF metals, particularly Cu, from jarosite whilst fixing sulfur is necessary before it is acceptable for HIsarna. This thesis evaluated several metallurgical approaches in removing the CEF metals from a locally sourced jarosite whilst fixing sulfur. The jarosite was sourced from Nyrstar (Budel, Netherlands) and is commercially known as Budel Leach Product (BLP). The BLP had a CEF concentration of 1.8 wt% which was substantially higher than the HIsarna limit (0.2 wt%); it also had a sulfur content of 9.3 wt%. The metallurgical approaches taken to treat the BLP included: hydrometallurigcal (acid, alkaline. ammoniacal and DES leaching); pyrometallurigcal (thermal decomposition and chloridisation); and a combined pyro- and hydrometallurgical approach (sulfur fixation with Na2CO3 with water washing). Ammoniacal leaching was the most effective hydrometallurgical approach in selectively removing Cu from the BLP, however, leaching efficiencies were low. Thermal decomposition resulted in an upconcentration of the CEF metals whilst releasing SO2 . Sulfur could be fixed with the combined approach, however, the presence of Na2CO3 converted any soluble CEF metal sulfates to insoluble oxides which increased CEF concentration. The most effective approach was the chloridisation of BLP which reduced the CEF concentration in the treated residue while fixing sulfur. Although the CEF concentration using the chloridisation approach (0.84wt%) was above the HIsarna limits, further refinement of the treatment strategy shows promise for utilising BLP in HIsarna ironmaking.

Aim of the blast furnace ironmaking process is the extraction of iron from iron ore, and prepare the raw iron (hot metal) for steel making. The iron oxides (ore) are charged into the furnace in the form of sinters and pellets containing the iron ore. Iron ore interacts with reducing gases and coke to form molten iron which in combination with slag are collected in the hearth of the blast furnace and tapped separately. Since blast furnace is a counter-current reactor, the permeability is of prime importance for its efficiency. When temperatures reach 1100 °C to 1200 °C the ore layers start to soften and gradually melt, and this region is called the cohesive zone. The cohesive zone consists of a series of approximate ring-shaped, doughnut-like masses of semi-molten, pasty ferruginous burden material. Here the loss of permeability is caused by melt onset and deformation of the solid phases due to the pressure of the burden. The shape and position of the cohesive zone affect the efficiency of the process and it is advantageous to have the cohesive zone located at as high temperatures as possible and its thickness as small as possible. This is governed by the properties of the pellets and sinter which in turn depends on the nature of ore or concentrate, associated gangue, type and amount of fluxes added, and their subsequent treatment. With the depletion of high-quality iron ore resources, the consumption of iron ores with high alumina (Al2O3) content is increasing. Therefore, it is important to investigate the influence of alumina on the reduction, softening, and melting behaviour of iron-bearing materials like sinters and pellets, hence its effect on the cohesive zone. This thesis explores the effect of alumina on the pellet’s behaviour in the cohesive zone, for which Reduction, Softening, and Melting apparatus (RSM) is used as a blast furnace simulator. With RSM, the pellet samples with similar basicity but varying alumina content are subjected to conditions similar to the blast furnace, and their reduction, softening, and melting behaviour are compared. It is observed that with an increase in alumina content the cohesive zone shifts to a lower temperature and its thickness increases, therefore the resistance offered to the gas flow increases. The alumina plays a multifaceted role, where it affects reduction degree, degree of carburization, the viscosity of primary slag, and finally wettability of slags with coke and iron. Alumina causes reduction retardation in heterogeneous conditions, due to the formation of low melting interfaces. This on one hand does not influence the total reduction degree but on the other increases the rate of homogenization of the pellet microstructure. Alumina induces reduction retardation in homogenous condition, by increasing the rate of melt formation due to an increase in the fraction of low melting phases. This causes an increase in the rate of softening and early melting. Degree of reduction is not the only factor that influences softening and melting behaviour, as a pellet sample with lower reduction degree and lower alumina showcase better softening melting properties than the pellet sample with a higher reduction degree and higher alumina content. Alumina acts as network former in the chemistries considered, increasing the viscosity of primary slag, hence increasing the resistance to gas flow. Alumina increases the proportion of high melting phases in the FeO lean slag. The possible effects of alumina on carburization and wettability are explored with the help of literature, one possibility is that alumina decreases the wettability of slag with iron shell, hence increases the degree of carburization causing early melting of iron shells. Simultaneously, the possible effects of basicity are also explored using literature; it seems with an increase in basicity the negative effects of alumina lessen.

Utilisation of reverts in sinter production is nonetheless challenging considering physical and chemical characteristics: physical by means of presence of extreme amount of fine material (<1mm) and chemical in terms of heavy metals, alkalis and uneven distribution of materials. Poor granulation, affecting permeability and degrading of cold strength of produced sinter are negatively influencing sinter processes. On the other hand, reverts contain valuable materials as carbon- and iron-bearing materials, and can affect the sinter process positively. Steelmaking companies generate large quantities of reverts, however the impact of reverts on sinter processes and sinter quality is not fully investigated. With this in mind, this study investigates the impact of revert blends utilised in sinter blend on sinter processes and quality.

During the production of steel, a dust waste stream is created that contains a significant amount of zinc which makes it difficult to treat and to recycle. Various furnaces have been developed that can deal with those dusts like rotary hearth furnaces and the DK process but none are fully optimal yet. HIsarna, a furnace in development by Tata steel, is able to treat those zinc bearing dust by separating zinc from iron whilst being an ironmaking furnace. Basic oxygen furnace (BOF) dust, blast furnace (BF) dust and historical oxy chalk sludge (HOKS) have been the dusts under investigation for recycling in HIsarna. BF dust is a source of zinc and carbon whilst both BOF dust and HOKS contain a large share of iron. Microgranulates have been made from BOF dust and HOKS with different additions of BF dust which provides carbon that can be used for reduction reactions. With the help of thermo gravimetric analysis (TGA) and a horizontal furnace for isothermal experiments at 1000°C and 1300°C, the best two microgranulates (one HOKS/BF dust, one BOF dust/BF dust) were chosen that could completely reduce all zinc and iron oxides in a nitrogen atmosphere. Because HIsarna has a reducing atmosphere, this thesis focuses on answering the question how the self reduction behaviour of zinc in the microgranulates compares to the reduction behaviour in an atmosphere of 50% CO and 50% CO2. It appears that during isothermal experiments at 1000°C, the zinc separates more efficiently in nitrogen than in the 50/50 atmosphere. However this was not seen at 1300°C. At this temperature, the zinc concentration in the BOF dust microgranulates decreased in similar ways in both atmospheres while the zinc in the HOKS microgranulates reduced much faster in this reducing atmosphere. Besides isothermal experiments, a vertical TGA furnace was used for a non-isothermal experiment up to 1500°C at a large enough scale to analyse the samples after treatment. However, not much difference in zinc reduction ability was found between the different atmospheres. The dust from those experiments was collected and showed to contain zinc and lead present in elemental form, oxides and carbonates as well as potassium chloride. The results show to be promising for the recycling of dusts in HIsarna.

Zinc smelters in the European Union are now facing a lot of problems, especially under the attack of the Covid-19. This study reviewed the situation of the zinc smelting industry in the EU, including production methods, application of raw materials, pollution control, and waste treatment. The vast majority of smelters use hydro-metallurgical process to obtain high-purity zinc products. Roasting – leaching – electro-winning method is well developed, accepting a large range of raw materials and also has economic advantages. However, the problem with this method is the generation of large amounts of leaching residues. Many researchers have been worked on this and proposed many solutions. It can be improved by increasing leaching efficiency and can better recover valuable metals from the leaching residues. As for environmental pollution in the zinc smelting industry, sulphur emissions have been under well control, and both waste water and solids can be partly recycled in the process. But the storage and disposal of leaching residues are the main problems that still exist and need to be resolved.

The main waste products of ironmaking at Tata Steel IJmuiden are CO2¬(g) and a solid waste stream consisting of mainly carbon and iron-bearing compounds. This solid waste is generally called Zn rich filter cake which contains too much Zn to be reintroduced into the iron making process. Besides Zn, Pb and Cd are also present. These filter cakes originate from the flue dusts that are expelled from the top of the blast furnace. Currently the solid waste is separated based on size distribution which allows the recycling of most of the materials and concentrates the heavy metals into the Zn rich filter cake. Previous research has shown that these cakes are resistant to regular leaching methods for selectively dissolving the contained heavy metals. This is due to their sulfide form. The methods that do work (such as acid leaching) also dissolve additional material such as iron, which is the main component of the waste stream. Therefore Tata Steel Europe is investigating whether alternative options are available to selectively extract these heavy metals and reintroduce the remaining material as secondary ore back to ironmaking.

In this research the option of adding oxidants with and without additional microwave treatment is investigated. Based on what is applicable in reality, literature and thermodynamic evaluations several oxidants were selected to oxidize the metal-sulfides to metal-oxides which can be readily leached in ammonia based media. Furthermore the material was characterized and an investigation was done on where the sulfur originates and whether this stream can be reduced or avoided. The quality of the results was verified by comparing the heavy metals dissolved into the leaching solution by ICP analysis and by determining the heavy metal content in the solid material before and after leaching with XRF. It was found that 98% of the sulfur originates from the blast furnace and only 2% from the addition of sodium sulfide at the water cleaning department.

Leaching experiments were done with a 40 °C leaching solution, a 5:1 liquid to solid ratio. Leaching solutions were all ammonia based due to its selectivity to heavy metals. Leaching the sample material without microwaving or addition of oxidants the highest Zn, Pb and Cd recovery was 54%, 0.5% and 24% respectively. Potassium permanganate as the oxidant resulted in the highest extraction of Zn at 67% in a 2M ammoniumsulfate, 9M ammonia leaching solution. Ferric chloride in a 2M ammoniumsulfate, 9M ammonia leach solution reached extractions of Zn and Cd at 64% and 45% respectively for the IJmuiden filter cake. For Pb the best extraction was 5% in a 2M ammoniumcarbonate, 9M ammonia leach solution with the same oxidants. Microwaving the sample during leaching resulted in a higher extraction for both Pb and Cd, whilst matching the non-microwave oxidant leaching extraction for Zn. The highest extractions were 61%, 42%, 83% for Zn, Pb and Cd respectively. Aging has also been proven to have an detrimental effect on the extraction of heavy metals, however the aging effect is negated when using microwave treatment or oxidants. Extractions for lab reactor leaching of fresh samples without added oxidants or microwaving with an ammonia sulfate solution, resulted in extractions of 62%, 0%, 40% for Zn, Pb and Cd respectively.

It has been verified that most of the sulfur comes from the blast furnace. Further it has been reaffirmed that the metal sulfides this sulfur forms are difficult to leach out. One study states that metal sulfides can and will form in the blast furnace. The current study supports that, even though no direct study of the blast furnace itself was done. Oxidants and microwave assisted leaching seem to work well for Pb and Cd, but are less effective on extracting a higher percentage of Zn. It is recommended to use this method in combination with another process, a different ironmaking process such as HIsarna would be preferable due to the reduction of ZnS to ZnO which is readily leached with an ammonia leaching solution.

HIsarna is a new furnace technology in the steel industry, featuring a large reduction of CO₂-emissions of up to 80%, and offering larger tolerances for gangue materials. Additionally, it has potential for zinc enrichment in the flue dust, as it can quickly vapourise zinc in the feed material and reject it to the flue dust. Increasing the zinc fraction in the flue dust up to 50% would allow for zinc recovery in the zinc smelters. The larger tolerances of the furnace make it possible to include material streams currently mostly land filled. In this thesis, the focus has been on three of these waste streams, goethite, Blast Furnace (BF) dust, and Basic Oxygen Furnace (BOF) dust. The research focussed on acquiring fundamental knowledge on the behaviour of these waste dusts at high temperatures and various retention times. This will aid their future use as an alternative feed stream material for enriching the HIsarna flue dust with zinc, without compromising the longevity of the furnace or the quality of the steel.
In a literature study, several alternative materials were investigated. Of particular interest are the sludge wastes from the steel industry for their large iron and zinc contents, the sludge waste from the zinc smelters for the same reason, and galvanised steel scrap, possibly in combination with EAF dust. There are a few challenges to overcome, such as the copper concentration in the zinc smelter residues, or the variation in composition and quality of steel scrap. However, these materials were identified as high potential for inclusion in HIsarna.  It was found that zinc can effectively be reduced and vapourised from the waste dusts regardless of its mineral form, in case there is carbon. The carbon acts as a reductant for the iron oxides, including zinc ferrite, and for zinc oxide. Goethite does not contain any carbon, however, mixing with BF sludge will allow the vapourisation of zinc. A model is proposed for estimation of the amount of carbon, and by extension BF dust, that is needed to achieve a full reduction of the iron oxides with native carbon sources. This will aid future mixing of these waste streams, allowing more control over the composition of the feed stream.
A competing mechanism to direct reduction of zinc oxide was identified. Zinc oxide can react with S₂ gas which forms during the thermal shock treatment, forming a zinc sulfide fine particle. At high temperatures, this intermediate species decomposes over time to release the zinc vapour, however, the exact mechanism could not be deduced from the experiments. The mechanism and timescale was verified at various temperatures, and holds up until 1300 ºC. The timescale shortens significantly when increasing the temperature. Therefore, from the work conducted, it was concluded that the zinc can be effectively removed at a relevant timescale for HIsarna and collected in the flue dust.

Cobalt is one of the most important critical raw materials for emerging technologies. There are many incentives for analysis of this metal, from increasing demand for rechargeable batteries, rising prices and social issues involved. This paper is the first attempt to perform a substance flow analysis of cobalt at a city level. The analysis resulted in a generic cobalt city flow model that can be adjusted for another CRM or city. The model is meant to help create a better, more accurate national, and subsequently EU level, analysis. The generic city flow model is the first step to extrapolate the bottom-up approach to get reliable results on a broader scale. A case study for the city of The Hague quantified the main cobalt flows within the city. Based on the results it was possible to suggest policy recommendations regarding critical raw materials at an urban level. The main recommendations were the lack of specific data from several sectors and the need for collaboration between governments, statistical offices and entrepreneurs. Those actors should work together to create a database accessible for researchers.